Air circuit breakers as described within U.S. Pat. Nos. 3,095,489 entitled "Manual Charging Means for Stored Energy Closing Mechanisms of Electric Circuit Breakers" and 3,084,238 entitled "Ratchet Mechanism for Charging a Closing Spring in an Electric Circuit Breaker" include operating mechanisms that are mainly exposed to the environment. Since the air circuit breakers are rated to carry several thousand amperes of current continuously, the exposure to convection cooling air assists in keeping the operating components within reasonable temperature limits.
Various accessory devices are used with such air circuit breakers to provide auxiliary function along with overcurrent protection. One such accessory is the bell alarm accessory that provides local and remote indication as to the occurrence of circuit interruption. U.S. Pat. No. 5,502,286 entitled "Bell Alarm and Lock-Out for High Ampere-Rated Circuit Breakers" describes a bell alarm accessory used with so-called "insulated case" circuit breakers wherein the circuit breaker interrupting components are completely enclosed within an insulating plastic enclosure. This patent describes one such bell alarm accessory that interacts with the circuit breaker operating mechanism to activate the bell alarm upon circuit interruption and to lock-out or prevent the closing of the circuit breaker contacts until the accessory is manually reset.
U.S. patent application Ser. No. 08/875,595 filed on 19 Jun. 1997 entitled "Circuit Breaker Bell Alarm Accessory with Lock-out" provides a bell alarm accessory that provides local as well as remote indication of such circuit interruption as well as preventing circuit breaker contact closure until and unless the accessory has become manually reset.
High-ampere rated air type circuit breakers operate in the range of 2500 to 5000 amperes such that the large circuit breaker operating components are arranged with the bell alarm reset components in a particular manner. When low-ampere rated air type circuit breakers that operate in the range of 150 to 1500 amperes require bell alarms with automatic lockout function, the arrangement of the circuit breaker operating smaller components do not readily allow the use of the high-ampere rated bell alarm reset accessory due to the lower mechanical forces generated within the lower rated circuit breakers. Especially in view of the requirement of a pair of switches, one for remote indication of the fault occurrence and another to provide the interlock function.
One example of an electric switch mechanism within relays and contactors that includes a slider intermediate a pair of contact springs to enhance operation of the switch mechanism is depicted in U.S. Pat. No. 4,983,788 entitled "Electric Switch Mechanism for Relays and Contactors".
It would be economically advantageous to use a common bell alarm accessory in different ampere-rated air circuit breakers without decreasing the size of the accessory components in accordance with the lower mechanical forces available at the lower ampere ratings.
One purpose of the invention, accordingly, is to describe a bell alarm accessory for common use with small-ampere rated air type circuit breakers of differing ampere ratings that allows automatic remote indication along with lock-out function upon response of the small-ampere rated circuit breaker operating mechanism to separate the circuit breaker contacts.